Egg parasitoids of the stink bug Edessa meditabunda (F) were studied on rattlepod Crotalaria spectabilis used in soybean crop rotation in Campo Novo do Parecis, Mato Grosso state, central western Brazil. Seven species of parasitoids were found: two Encyrtidae, one Eurytomidae, and four Platygastridae. The occurrence of Trissolcus euchisti (Ashmead) and Trissolcus elimatus Johnson (Platygastridae) on eggs of E. meditabunda is recorded for the first time. Moreover, this is the first record of T. elimatus and T. euchisti from Brazil.

Stink bugs (Pentatomidae) are the most important pests of soybean (Glycine max) due to their high population densities and damage to seeds (Côrrea-Ferreira & Panizzi 1999, Belorte et al 2003). Edessa meditabunda (F.) is a stink bug that occasionally causes significant damage to soybean in Rio Grande do Sul state and in central western areas of Brazil (Corrêa-Ferreira & Panizzi 1982, 1999, Panizzi 1997). Edessa meditabunda can also feed and breed on alternate hosts or occupy overwintering sites. Most of the studies on the field biology of phytophagous stink bugs concentrate on crops, paying less attention or completely overlooking the role of wild plants in insect population buildup (Panizzi & Parra 2009).

The rattlepod Crotalaria spectabilis (Leguminosae) is commonly used as green coverage in soybean crops, and is important for nitrogen fixation, higher soil organic matter, and microbial activity (Gravena 1992, Kushida et al 2003). Studies are needed to determine the potential of this plant as a shelter to improve native populations of egg parasitoids of phytophagous stink bugs.

Biological control is an alternative to reduce populations of stink bug pests on target crops. Hymenopterous egg parasitoids are probably the most important among the complex of natural enemies of stink bugs. In soybean, Trissolcus basalis Wollaston and Telenomus podisi Ashmead (Hymenoptera: Platygastridae) are the main species attacking their preferred hosts, Nezara viridula (L.) and Euschistus heros (F.), respectively (Corrêa-Ferreira & Moscardi 1995, Medeiros et al 1997). Management of the green coverage that serves as alternative hosts for stink bugs can also be beneficial to increase natural enemy populations (Altieri 1989). Thus, in the present study we evaluated the natural occurrence of parasitoids on E. meditabunda eggs found on rattlepod crops, in Campo Novo do Parecis, Mato Grosso state, central western Brazil.

During September 2009, eggs of E. meditabunda were collected on rattlepod at the Fazenda São Paulo (S 13°06'54" W 57°57'14") in a 2 ha area (near a forest remnant) and taken to the laboratory. Egg masses were individually placed in Petri dishes, and kept at room temperature (26 ± 2°C; photophase 10h) until emergence. Seven species of parasitoids were identified from eggs of E. meditabunda: Ooencyrtus submetallicus (Howard) and Ooencyrtus sp. (Encyrtidae); Neorileya albipes Girault (Eurytomidae); and Gryon sp., Trissolcus urichi Crawford, Trissolcus elimatus Johnson and Trissolcus euchisti (Ashmead) (Platygastridae). Trissolcus elimatus and T. euchisti are recorded for the first time from Brazil, and E. meditabunda is a new host record for both parasitoid species (Orr et al 1986, Johnson 1987). Trissolcus urichi, Ooencyrtus sp. and Neorileya sp. were previously reported parasitizing E. meditabunda and several other species of pentatomids on soybean in Paraná state, southern Brazil (Corrêa-Ferreira & Moscardi 1995). Ooencyrtus submetallicus had been already reported on eggs of E. meditabunda in Brazil (De Santis 1985).

Acknowledgments

To Cooperativa Aliança dos Produtores do Parecis (CAAP) for both financial and logistical support. To Fundo de Apoio à Cultura da Soja (FACS) for funding.